In this share equipment grant application, we propose to purchase and validate a high performance multichannel electrophysiology recording/stimulation system for free behaving mice and rats performing behavioral tasks. The utility of this equipment is to extend our current neurobehavioral core facility in assessing brain activity while performing behavioral tests. As a group of investigators at the SFVAMC interested in stroke, traumatic brain injury and neurodegeneration, we are seeking an in-vivo correlate of CNS function. To determine functional outcome after brain injury or degeneration and respective treatment, we have built a neurobehavioral core facility that provides a comprehensive battery of motor and cognitive function tests. However, these tests are still not specific enough to decipher the exact brain circuit involved in behavior, neither are they sensitive enough to detect neuronal impairment at the cellular resolution. We propose to incorporate large-scale neural recording in freely behaving mice and rats performing behavioral tasks because large ensemble recordings are critical for functional circuit mapping. The proposed system is capable of processing up to 512 channels of data, with matching-channel headstages for freely moving rodents capable of recording up to 512 channels. With the ability in simultaneously recording neural activity and sensing behavior, this system can also allow precise control of neural circuit of interest using closed-loop stimulation and/or with optogenetics techniques, to tease out specific circuitry or type of oscillation involved in brain injury or being targeted in therapy. This cutting-edge multichannel electrophysiology recording and stimulation system will not only better our understanding in how brain injury/degeneration affects neural circuits, but also will extend our research programs in finding therapeutic interventions for these disorders that commonly afflicting our veterans.